A recent drastic development in an information network or multimedia processing demands an optical communication system capable of transmitting a great amount of data. A typical optical communication system requires a number of small-sized, high-speed, and highly reliable optical switches for a line switching operation in an emergency and also for a private branch exchange system, which has resulted in an increased development of such optical switching devices.
FIG. 20 shows a perspective view of a conventional optical switching device, disclosed in the International Conference on Optical MEMS (Micro Electro Mechanical Systems) and Their Applications. The optical switching apparatus includes four optical fibers 201, 202, 203, and 204. Also provided in the apparatus are a movable mirror 205 coated with a conductive material for routing light, a wire 206 for supporting and biasing the mirror 205 so that it takes a horizontal position, an insulating layer 207, and a pair of electrodes 208.
With the optical switching device shown in FIG. 20, when the mirror 205 is located in the vertical position by an electrostatic force generated by the application of a voltage to the electrodes 208, light emitted from the optical fiber 201 is reflected by the mirror 205 into the optical fiber 204. Light emitted from the optical fiber 202 is also reflected by the mirror 205, where it is oriented into the optical fiber 203. When the electrostatic force is turned off and thereby the mirror 205 returns to the horizontal position, light emitted from the optical fiber 201 directly enters the optical fiber 203. Light emitted from the optical fiber 202 also directly enters the optical fiber 204.
FIG. 42 shows, in perspective view, another prior art optical switching device, generally indicated by reference numeral 700. The device 700 has a housing 702. The housing has side walls 704A, 704C, 704D and 704F supporting optical fibers 706A, 706C, 706D and 706F, respectively. Provided at the center of the housing 702 is the mirror 708, which is moved between two positions, indicated by solid and dashed lines, by an electrostatic linear motor (not shown).
With the optical switching device, when the movable mirror 708 takes the solid-line position, light emitted from the optical fiber 706A is reflected by the movable mirror 708 and then directed toward the optical fiber 706F. Also, light emitted from the optical fiber 706C is reflected by the movable mirror 708 and then directed toward the optical fiber 706D. When the movable mirror 708 is, on the other hand, in the dashed line position, light emitted from the optical fiber 706A is transmitted into the opposing optical fiber 706D. Also, light emitted from the optical fiber 706C is guided into the opposing optical fiber 706F.
With the first prior art optical switching device, a wire is used for supporting the light-routing mirror, and electrostatic force for driving the mirror. However, the wire is fixed at both its ends by a supporting member, which requires torque to rotate the wire about its axis so that it might be difficult to move the mirror to the desired position, and power should always be supplied to hold the mirror in the vertical position.
Also, in the second prior art switching device 700, optical fibers 706A, 706C, 706D and 706F extend out of the housing 702 in four directions, which requires a larger space for mounting. In addition, the electrostatic linear motor used for driving the movable mirror 708 should always be supplied with power for maintaining the solid-line position.
Furthermore, neither of the optical switching devices has a mechanism for detecting the position of the mirror, which prevents checking whether the device functions correctly. This in turn results in a system having the switching device that can not self-detect a malfunction, which decreases reliability. In addition, light emitted from one optical fiber is designed to be directly received by the associated optical fiber, rather than being concentrated by an optical element such as lens. This results in a significant part of the light from the one optical fiber failing to be transmitted into the associated optical fiber due to a possible offset of the optical fibers. Furthermore, the optical fiber is shaped at its end opposing the associated optical fiber to form an end surface perpendicular to a longitudinal axis of the one optical fiber, which reflects and returns a major part of the light at the end surface.